Just to clear of course I would not try to cash an unsigned check. But, I wanted to ask that if a person receives an unsigned check for services they provided and tried to cash it, what would happen? Is there a penalty? What if a person writes a swigglely line on the signature part of the check because they did not want to go through the trouble of having it signed and returned? Is there a penalty for that if caught? Remember, the client intended on giving this check to the person providing the services, it is legitmate. It just was not signed.

I would send the check back to the payor. Trying to sign the payor's name is fraud. In any case, the bank wont let you deposit a check that is not signed. I dont think that the client's intent is relevant.